Mercury is an excellent conductor of electrical current. This toxic element was used extensively in the electrical control mechanism of thermostats. Approximately three ounces of elemental mercury sealed in a glass ampoule with metal electrical conductors serves as the active control device in thermostat mechanisms. The ampoule is attached to a wound bi-metallic strip that contracts and elongates in proportion to temperature variations. The mercury-containing thermostat serves as a primary control for contactors that in turn provide power to HVAC and/or industrial process equipment. Improvements in electronic control system technology have rendered mercury-containing thermostats inadequate for state-of-the-art mechanical equipment control. Many of these antiquated mercury thermostats are still in use and are being replaced as systems become too costly to operate and maintain.
Mercury contained in old thermostats is likely to be released into the environment if the glass ampoule is mishandled. Disposal of mercury-containing devices in municipal solid waste collection is forbidden by state and federal law. Mercury-containing thermostats are regulated as universal waste and are the responsibility of the generator at the time the device is considered a waste material.
Mercury Thermostat Recycling
Full Title: Thermostat Recycling Corporation
Full Title: Earth 911
Regulations Affecting Thermostats
Full Title: Universal Waste Rule
Full Title: Removal and Recycling of Mercury-Containing Products from Structures to be Demolished
N.C. Division of Environmental Assistance and Customer Service • Mailing Address: 1639 Mail Service Center, Raleigh, NC 27699-1639 • Physical Address: 217 W. Jones Street, Raleigh, NC 27603 • Toll Free: (877) 623-6748